Reversible active bridging sulfur sites grafted on Ni3S2 nanobelt arrays for efficient hydrogen evolution reaction

Elaborate and rational design of cost-effective and high-efficiency non-noble metal electrocatalysts for pushing forward the sustainable hydrogen fuel production is of great significance. Herein, a novel VS₄ nanoparticle decorated Ni₃S₂ nanobelt array in-situ grown on nickel foam (VS₄/Ni₃S₂/NF NBs) was prepared by a self-templated synthesis strategy. Benefitting from the unique nanobelt array structure, abundant highly active bridge S₂^2- sites and strong electronic interaction between VS₄ and Ni₃S₂ on the heterointerface, the integrated VS₄/Ni₃S₂/NF NBs exhibited excellent electrocatalytic hydrogen evolution activity and robust stability. The density functional theory (DFT) further revealed the reversible conversion catalysis mechanism of bridging S₂^2- sites in VS₄/Ni₃S₂/NF NBs during HER process. Notably, bidentate bridging SS bonds as the predominant catalytically active centers can spontaneously open once H adsorbed its surface, leading to the aggregation of negative charges on S atoms and thus facilitating the generation of H* intermediates, and spontaneously close when H* desorption is going to form H₂. Our work provides fresh insights for developing potential polysulfides as high-performance hydrogen-evolving electrocatalysts for prospective clean energy production from water splitting.

In-situ construction of superhydrophilic crystalline Ni3S2@amorphous VOx heterostructure nanorod arrays for hydrogen evolution reaction with industry-compatible current density. Dalton Trans 2022;51:7234-7240. [DOI: 10.1039/d2dt00157h]

The synergistic effect of high active surface/interface and optimized electronic structure of electrocatalysts is of great significance to improve the performance of hydrogen evolution reaction. Herein, a superhydrophilic core@shell heterostructure...

Controlled Synthesis of V-Doped Heterogeneous Ni3S2/NiS Nanorod Arrays as Efficient Hydrogen Evolution Electrocatalysts

The development of low-cost and high-efficient electrocatalysts toward hydrogen evolution reaction (HER) is highly desirable and challenging. Herein, the novel V-doped Ni₃S₂/NiS heterostructure nanorod arrays grown on nickel foam (VNS/NF-WM) are synthesized via a facile methanol-assisted hydrothermal method. We demonstrate that the morphology, phase composition, and crystallinity of VNS/NF are well modulated by tuning the ratios of water/methanol solvent. The optimized VNS/NF-WM-heterostructured nanorod (volume ratio of water/methanol is 3:1) exhibits superior HER electrocatalytic activity with low overpotentials of 85 and 218 mV to yield current density values of 10 and 100 mA cm^-2, respectively, meanwhile sustaining an excellent stability with almost an unchanged current density of 10 mA cm^-2 for 60 h. Our work offers fresh insights into the rational design of highly active and stable earth-abundant-heterostructured electrocatalysts for the hydrogen fuel production.

Generation of Ni3S2 nanorod arrays with high-density bridging S22- by introducing a small amount of Na3VO4·12H2O for superior hydrogen evolution reaction

Bridging S22- moieties have been demonstrated to be highly active sites existing in metal polysulfides for the hydrogen evolution reaction (HER), thus the incorporation of high-density bridging S22- into a Ni3S2 material to improve its electrocatalytic HER performance is highly desirable and challenging. Herein, we report a novel Ni3S2 nanorod array decorated with (020)-oriented VS4 nanocrystals grown on nickel foam (Shig-NS-rod/NF) via a simple and facile solvothermal method. Results show that the in situ incorporation of VS4 not only triggers the formation of such a nanorod array structure, but also contributes to the uniform grafting of high-density and high catalytically active bridging S22- sites on the interface between Ni3S2 and VS4 for enhanced HER activity, and also promotes the absorption ability of OH- radicals and thus accelerates the HER Volmer step in alkaline media. As expected, the resultant Shig-NS-rod/NF material exhibits impressive catalytic performance toward the HER, with a much lower overpotential of 137 mV at 10 mA cm-2 and a long-term durability for at least 22 h, and is superior to Ni3S2 nanorod arrays with low-density bridging S22- (Slow-NS-rod/NF) and NS-film/NF counterparts (without VS4), even outperforming the NF-supported 20% Pt/C at a large current density of over 120 mA cm-2. Our findings put forward fresh insight into the rational design of highly efficient electrocatalysts toward the HER for green hydrogen fuel production.

Stabilization of two conformers via intra- or inter-molecular hydrogen bonds in a dinuclear vanadium(v) complex with a pendant Schiff base: theoretical insight

A dinuclear vanadium(v) complex, (μ-O)₂[V(O)(L)]₂, [where HL = 2-methoxy-6-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol] has been synthesized and characterized by spectral and elemental analysis. A single crystal X-ray diffraction study confirms it structure. Two different conformations, stabilized via either intra- or inter-dinuclear hydrogen bonding interactions, co-exist in the solid-state structure. The energies of these intra- or inter-dinuclear hydrogen bonding interactions have been estimated by Density functional theory (DFT) calculations. A ‘Non-covalent interaction’ (NCI) plot has also been used to characterize these interactions.

Two different hydrogen bonded conformers coexist in a synthesized dinuclear oxovanadium(v) Schiff base. Density functional theory (DFT) calculations were utilized to calculate the energies involved in two different conformers.

New Lanthanide Mixed-Valent Vanadium(III/IV) Oxosilicates, Ln4V(5-x)Zn(x)Si4O22 (Ln = La, Ce, Pr, and Nd), Crystallizing in a Quasi Two-Dimensional Rutile-Based Structure

A family of lanthanide mixed-valent vanadium(III/IV) oxosilicates Ln4V(5-x)Zn(x)Si4O22 (Ln = La, Ce, Pr, and Nd) was synthesized as high-quality single crystals via a high-temperature molten salt method. An in situ reduction of V(V) to V(III/IV) as well as of Ce(IV) to Ce(III) was achieved utilizing Zn metal as the reducing agent, some of which is incorporated into the crystal structure. Ce4V(4.77)Zn(0.23)Si4O22, to the best of our knowledge, is the first example of a cerium-containing mixed-valent vanadium silicate. The crystal structures were determined by single-crystal X-ray diffraction, and the four isostructural oxosilicates were determined to crystallize in the chevkinite-structure type in the monoclinic space group I2/a. The unit cells of the Ln4V(5-x)Zn(x)Si4O22 (Ln = La, Ce, Pr, and Nd) series are related to the reported C2/m phases Ln4V5Si4O22 (Ln = La, Pr, and Nd) by a doubling of the c-axis and a loss of a mirror plane. The three-dimensional crystal structure consist of two-dimensional rutile-based vanadium oxide and lanthanide oxide layers linked via Si2O7 groups. The temperature dependence of the magnetic susceptibility of these compounds was measured, and only the Nd analogue exhibited a magnetic transition at 5 K; all samples displayed a discontinuity or deviation from linearity at ca. 130-150 K.

Synthesis, crystal structure and thermal properties of Ca6(C12H14O4)4(CO3)(OH)2(H2O)x--a 3D inorganic hybrid material

The inorganic-organic compound Ca(6)(1,3-adamantanedicarboxylate)(4)(CO(3))(OH)(2)(H(2)O)(x) with 0 < x < 15.2 was synthesized by hydrothermal methods. The crystal structure was determined on the basis of high resolution synchrotron powder diffraction data and poly-crystal measurements. The crystal structure of Ca(6)(C(12)H(14)O(4))(4)(CO(3))(OH)(2)(H(2)O)(14) is tetragonal, space group I4(1)/amd (141) with a = 29.12 Å, c = 15.85 Å, V = 13,440 Å(3) and Z = 8. The compound is classified as a 3D inorganic hybrid material with a 3-dimensional inorganic framework consisting of Ca and O, connected to 1,3-adamantanedicarboxylate anions. The structure shows hydrophilic channels in a diamond-like network. In between the channels there exist hydrophobic pores with surfaces defined by adamantane cages. The shortest distance between hydrogen atoms from different molecules in these pores is 3.6 Å. The largest hydrophilic cavity has a diameter of 10 Å and the pores connecting the channels have a diameter of 5 Å. In the as-synthesised state these channels are filled with water molecules. Reversible dehydration-rehydration occurs. The dehydrated compound easily takes up water from ambient air.